First things first, you will need MP4 files of what you want to put into the game. Then open the games local files and go down this path:

Fuser/Fuser/Content/Movies

Next:
Go through one of the six folders present (or the other intro logos just outside the folders) and rename the MP4 file to the exact file name of what you are replacing.

And then, you are done! (provided you didn't mess up the naming)

Example of what it would look like:

(Update 2/20/2023: just realized i forgot to mention that diamond store got fixed lol. new link)

Okay so, you will first need to download the following DLL:
https://github.com/NarrikSynthfox/FuserSongLoader/releases/tag/diamond_shop_fix (trust me, it is safe)

Next, you will have to open your local files again and go down this path:

Fuser/Fuser/Binaries/Win64/

Insert the DLL and then go down the following path:

Fuser/Fuser/Content/Paks

You will then need to create the following folder with this exact name:

"custom_songs"

Run the game to ensure the DLL is working. Please note that currently, it disables the ability to add Diamond Store songs into your crate however pre-added ones will still be there.

Next, either look on the official subreddit for the spreadsheet of songs, or create your own. In the case of downloading, put the folder given into custom_songs and extract the contents.

Run the game and locate the custom song in the crate to ensure it is not broken.

After running the game, delete the newly created files "customSongsUnlocked_P.pak" and "customSongsUnlocked_P.sig" if you want to insert another custom song, as that may cause either the game to crash or the custom to be locked from use.

Example of using custom songs in-game:

(customs taken from FUSER Customs Spreadsheet)

(UPDATE: 3/9/2023: Slightly late to this again, but there is now cover art, risers, pickups and keyzones available! I have updated the link to be the latest version.)

First, you will need to install the custom song creator version 2.0.1 from the following page:
https://github.com/NarrikSynthfox/FuserCustomSongCreator/releases/tag/v2.0.1 (trust me, this is safe)

Next, you will need the stems of a song. These can be a little hard to find, however there are various websites which you can source from, or you could do your own AI separated stems through MVSep, or the Ultimate Vocal Remover GUI to run on your own computer provided it is strong enough.

MVSep
https://mvsep.com

Ultimate Vocal Remover GUI
https://github.com/Anjok07/ultimatevocalremovergui

Another option for stems is to find cover/remake stems. You can find those on various websites, or you could do it yourself if you have the instruments necessary. Below are the most trusted sources for remake stems.

Karaoke Version
https://www.karaoke-version.com

JamKazam
https://jamkazam.com

Finally, you will need a Digital Audio Workstation (DAW). It is not recommended to use Audacity, but instead to use a program such as REAPER or a free trial version of FL Studio/Ableton. Also, for Major/Minor keys, it's recommended to use Melodyne for it.

REAPER
https://www.reaper.fm

FL Studio
https://www.image-line.com

Ableton
https://www.ableton.com/en/trial/

Melodyne
https://www.celemony.com/en/start

As an extra thing, a FUSER custom song template for REAPER has been released by community member and spreadsheet owner SheepQueen, which assists with structure, pickups and risers.
https://drive.google.com/file/d/1QryIIMRoWVxre2LXD8qDviHeiDCDlf7k/view?usp=share_link

If your song does not have leaked stems, run it through the MVSep website or another website/program which uses an AI stem separator such as Spleeter or Demucs.

After getting all the proper software and stems needed to create a custom song in FUSER, start by figuring out the BPM and key of the song. You will need to look at use music theory, or look at several different sources. Anything AI based (such at Tunebat!) is likely a bad source for the info, as computers aren't advanced enough to know music theory.

If it is from Rock Band/Guitar Hero stems, you can optionally run it through a charting program such as EOF to see the hopefully consistant BPM however key would likely be left out of that data.

After determining the key and BPM of a song, you must put all the stems of the song at the very start of the first measure and cut down the song until it is exactly 32 bars and loops cleanly. I cannot describe in detail how to do this, as it is different for every song. However, some ground rules are that you should line up song section changes every 8 bars, or 4 bars if it is unavoidable.

After doing the loop, you may consider doing a riser along with it. This is necessary to be considered a complete custom. To create a riser, you need to do a 4 bar fade-in along with optionally a 1-2 bar post-riser ending. For an easy guideline to the riser, see a template above.

You must then export each stem out of the program individually as .ogg files. If a stem is in separate parts (drums having more then one audio file), export them together. Optionally, you may need to separate the pitched and unpitched audios, for keyzones later.

After the hard part of actually creating the loop, you need to then open the custom song maker.

Select "Create New Custom Song" from opening it up, and select and fill in the following page with all of the required info:


Afterwards, select all of the Song Cell areas (beat, bass, loop, lead), and put in the stems plus the instrument info. If you don't have a stem for one particular part, you don't need to insert that one however it will still appear as a 4 stem song.

For pickups, it is a system of 0-128, with each number being a quarter note. It depends on the song with what you highlight with a pickup, but be reasonable and do not put pickups on 0 and 128 as those aren't able to be used in-game. It should also be noted that the pickup system is also used for preview audio, where pickups between 124 and 128 are used to play the audio slightly early.

Now, let's get into the real deal of Advanced Mode. This is used when you want more then two audio files to play at once, usually to swap between pitched audio, unpitched audios, and instrument audio like a horn or guitar solo. This will require you to export with that in mind, having separate audios.

For simplicity sake, the only things you will need to mess with are the keymap presets, which are Major for the Major key, Minor for the minor key, and Shared for both or duplicated. Add as many audio tracks as you need, assign the audio to a specific keyzone, and you will golden to ensuring that it works upon opening the game.

To test your custom to see if it entirely usable, do the following things:

Put the song's drum (or another stem that is being used as rhythm) up against a base game drum as a metronome, such as Crystal Beach, Blinding Lights, or Satisfaction.

Double check the key to see if it correct, or if the song is multiple keys.

I hope what you learned from this will help you mod FUSER to it's max capabilities. Also it was fun to spend my 2 am on something other then just videos.